Electrical terminal



Aug. 10, 1937. J. H. INGMANSON ELECTRICAL TERMINAL Filed .June '50, 1955 FIG.

INVENTOR J. H. INGMANSO/V ATTORNEY Patented Aug. 10, 1937 UNITED STATES PATENT OFFICE Bell Telephone Labor York, N. Y., a corpor Application June 30,

3 Claims.

This invention relates to electrical terminals and more particularly to the sealing of condensers in suitable containers.

In the manufacture of condensers, particularly those in which the condenser units are of the socalled paper-wound type, it is the customary practice to place the impregnated unit in a container wherein it is surrounded with a potting compound to prevent the entrance of moisture. A layer of sealing compound having a relatively high melting point is also usually placed over the potting compound to prevent escape or damage to the latter and the terminal leads of the condenser are brought up through and 'sealedby these compounds. While such a method of sealing is a satisfactory operation under normal conditions, it is not satisfactory for use with condensers which are subjected to high temperatures, as for example, condensers used in certain 20 radio and sound picture fields. When the temperatures in service are of the order of the melting point of the impregnating compound, the latter tends to mix with the potting compound, resulting in a mixture, the resistivity of which 25 is lower than that of either. the impregnating compound or the potting compound, and thus lowering the insulating resistance of the condenser. This commingling of the impregnating and potting compounds also takes place to a certain ex- 30 tent during the pouring of the potting compound unless special precautions are taken. Also at lower temperatures there is a tendency for the potting compound to crack, thus permitting the entrance of moisture into the condenser and caus- 35 ing lowered resistivity.

It is, therefore, anobject of the present invention to overcome the difficulties experienced in the potting of condenser units and to bring out the terminal leads from the container without 40 permitting the entrance of moisture therein.

Another object of this invention is a condenser which will operate satisfactorily even when subjected to temperatures in excess of the melting point of the impregnating compound and irrespective of the position in which it is mounted.

These and other objects of the invention are attained by encasing the condenser units in an air-tight container and bringing out the terminal leads through metallic tubes which are soldered or otherwise sealed to the casing in such a manner as to insure a moisture and gas-tight joint. The terminal leads which are insulated with a high grade of vulcanized rubber or a similar insulating material possessing high elasticity and 5 long life are positioned within the tubes and the atories, Incorporated, New ation of New York 1933, Serial No. 678,361

latter are reduced to a smaller diameter over a greater part of their length, thus causing compression of the elastic insulating material and as a result a joint which is moisture and gas-tight. Under certain conditions, as for example condensers not subjected to high temperature, the potting operation may be eliminated altogether, while in the case of condensers which are subjected to temperatures comparable to the melting point of the impregnating compound, the container after the unit is positioned is completely filled with the impregnating compound and then hermetically sealed. In the latter case there is no appreciable change in the electrical characteristics of the condenser even though the impregnating material is liquefied and furthermore the condenser may be mounted in any position without difiiculty.

The invention may be more clearly understood by reference tothe accompanying drawing in which, I

Fig. 1 is a view in perspective of an embodiment of the invention; f

Fig. 2 is a front elevation of the condenser of Fig. 1 with a portion of the container cut away to show the method of bringing out the terminal leads; and

Fig. 3 is a partial view showing a modified structure.

Referring more particularly to Figs. 1 and 2 there is disclosed an electrical condenser provided with a container consisting of a lower portion or can 5 and a cover 6, the two portions being joined together at l by soldering or similar means to insure an air-tight container. The condenser unit 8 is positioned within the container so that its terminals are adjacent the lower portion of the can, and terminal leads 9, 9 are connected to the terminals of the condenser unit. Each of the terminal leads is insulated with a covering ID of soft rubber or similar elastic material, such for example as Duprene or rubber 'I'hiokol and is then threaded through a tube i i the inner diameter of which is substantially that of the outer diameter of the insulated wire. The middle portion of this tube is then decreased in diameter as by a drawing or a rolling operation so that in this portion the insulating medium is under compression between the terminal lead and the inner wall of the tube, thus insuring an airtight seal. Each of the tubes H passes through a suitable perforation in the cover and is soldered thereto as at l2 to insure an air-tight seal at this point. The outer end of the terminal leads 9 is formed into an eyelet I3 to facilitate soldering connecting leads thereto. A standard form oi. mounting lug I4 is provided to permit mounting the condenser unit on racks in the standard manner.

In assembling this condenser, terminal-leads are threaded into metallic tubes oi suitable dimensiom, these tubes being preferably cut from copper tubing which has previously been coated with tin or solder in order to avoid any deteriorating eflect of copper on the rubber. The tubes are then rolled down tightly over the rubber tor the greater portion of their length to prdvide the necessary compression to insure an air-tight seal but leaving at each end a portion approximately one hall inch long which is maintained at its original diameter in order to prevent excessive bulging of the rubber. The leads are next soldared to the condenser terminals and the tubes are held in position by a wrapping ll of thread which binds the tube to the condenser unit. The tubes arethen threaded through perforations in the cover and are soldered thereto to insure an air-tight seal. The unit is then placed in position within the container and the cover is soltiered or braced to the can. Instead or using a separate tube for each terminal lead it may be desirable under certainconditions to place two or more insulated leads inthe same tube which isxthen drawn down to provide the necessary compression to insure a tight seal.

In case that the condensers are not to be used under service conditions where the temperature exceeds the melting point 01' the compound used to impregnate the condenser units, no potting opand secured thereto by means of an adhesive I, such as asphaltic cement. The terminal wire extends to the top 0! the bushing and is connected to a suitable soldering terminal it. This construction is used for condensers which are to be subjected to high potentials in order to minimise the danger of surface leakage.

Whatisclaimedis: v x

1. A terminal member-comprising a metallic tube and a terminal lead insulated with an elastic medium extending therethrough, said tube extending over substantially the entire length of said insulated lead, the inner diameter oi said tube at its ends being substantially the outer diameter of the insulated terminal lead and the inner diameter of the middle portion of said tube being less than the outer diameter of the insulated terminal lead whereby the elastic insulation is compressed over the greater portion of its length to provide an air-tight seal.

2. A terminal member for use with electrical apparatus mounted in an air-tight container comprising a metallic tube adapted to be hermetically sealed in the container, a terminal lead insulated with, an 'elastic medium positioned within said tube, the length of said tube being only slightly less than the length of said insulated terminal lead, the middle portion of said tube for a greater portion or its length being reduced in diameter to such an extent as to cause compression of the elastic medium against the walls of the tube and means for hermetically sealing said tube to said container at one 01 the unreduced portions 0! said tube thereby insuring 

